Pressure gauge



"June 23, 1931. H. A. CLARK 1,811,173

PRESSURE GAUGE Filed March 29, 1928 M H Mun INVENTOR Mt ATTORNEY Patented June 23, 1931 UNITED STATES PATENT OFFICE HERBERT A. CLARK, OF ROCHESTER, NEW YORK, ASSIGNOR TO TAYLOR INSTRUMENT COMPAN'IES, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK PRESSURE GAUGE Application filed March 29, 1928.

1 usually mercury in a tube closed at one end is balanced against the pressure to be 5 measured.

Instruments ofthis type have one con- 'siderable disadvantage: During shipment, when .the column may be in a horizontal position, air may find its way to the end or top of the column and thereby destroy the value of the instrument. It is a common practice to have the outlet of .the mercury tube so disposed in the well that the outlet 1s immersed in theliquid irrespective of the position of the instrument. However, heavy shocks and vibrations often cause a displace- 'ment of the liquid so that air contained 1n the well can enter into the tube and creep to the closed end of the tube.

It is the object of the present invention to practically eliminate this danger and to providea. gauge construction in which a positive seal may be provided against entrance of air into the tube containing the column of liquid.

.In order to fully explain the inventlon and the principal points of novelty involved, reference is made to the accompanying drawings, which represents a section through a device embodying the inventlon, 1n the particular. instance an absolute pressure gauge. In the drawings, 1 represents a glass tube normally containing mercury or other su table liquid. The tube 1 is connected atits bottom with a well 2 by means of a crook portion 1a. The well 2 is preferably an iron casing since iron is chem1cally immune against mercury. The connectlon between the crook portion of the tube and the well 2 is made by means of a suitable union 3. The well has an outlet 4 through which it may be connected with the atmosphere or any other gas of which the pressure is to be measured.

The mechanism thus far described represents a typical construction in general use.

The invention consists in mechanism operable at will to positivelyseal the tube against leakage of air or other gas into the column of liquid.

To this end I have provided as part of the Serial No. 265,745.

well 2 and depressed from the bottom thereof, a depression or auxiliary chamber 5 for cooperation with a piston 6 disposed for movement into and out of the chamber 5. The chamber 5 and the piston 6 are so accu rately machined and fitted that the interspace between the two does not permit mercury to flow through it. Thus, when the piston is lowered into position in the chamber against the mercury contained therein, air can not come into contact with the mercury, but finds a solid-filled mercury column: positively barring flow into the column irrespective of the position of the tube.

The piston 6 is preferably supported from the top of the well and made adjustable in vertical direction by means of a screwthreaded shank 7 co-operating with a correspondingly screw-threaded bore 8 or any other equivalent means. the shank 7 may be provided with a screw driver slot, as'indicated, or any other means for effecting turning movement of the shank.

In order to provide for expansion and con-- traction of the mercury confined in the column by means of the piston 6, I provide the latter with means for resiliently pressing upon the mercury. lVhile there are various means available for this purpose, I make the piston of two component parts movable relatively to each other in axial direction and provide spring means 9 tending to move the parts away from each other. I preferably provide the part 6a with a bore and the part 6?) with a tenon 6d loosely fitting the bore 60, the compression spring 9 being mounted 011 the tenon 6b and bearing upon the opposing surfaces of the parts 6a and 6?). To prevent separation of the parts 60 and 6b, the tenon 6d may be provided with a groove 66 and the part 6a with a set screw 6 for engagement With the groove 66.

The outlet 4: and the bore 8 have closures 4a and 8a respectively for tightly sealing the openings against loss of mercury during shipment. v

The operation is as follows: The tube 1 is normally completely filled with mercury and the surface to be acted upon by the air or gas, i. e. the level of the The upper end of mercury is in the well. For shipment of the instrument, the closure 8a is removed and by means of a screw-driver or wrench the shank 7, which, of course, has a recess for engagement by the screw-driver or the wrench, is turned to lower the piston into the chamber 5. The piston moves freely until the piston enters the chamber 5 and forms a seal. Since the mercury is incompressible, the piston can move no farther and continued movement of the shank 7 and part serves to compress spring 9. lVhile the temperature remains the same, the piston will remain the same. lVith increase of temperature, part of the r confined mercury is forced out against the resistance of spring 9. With decrease of temperature, the piston, under the action of spring 9, follows the receding mercury.

However, I prefer to carry out the operation in slightly different form. I first evacuate the well until the top of the column in tube 1 is depressed to a point a small distance from the end of the tube and in this condition I lower the piston into the chamber 5. Now, by continuing the downward movement of the shank 7, the piston can advance in the chamber until the columnagain completely fills the tube and then the movement of the shank is continued until the spring 9 has been compressed to the desired degree. d

The dimensions of the chamber 5 and the spring 9 are such that the head surface of the piston remains within the chamber for all temperatures within the range chosen. The degree of evacuation preparatory to the operation of the piston, is then so chosen that the head surface of the piston initially assumes a position within the chamber 5 approximately corresponding to the surrounding temperat-ure. Thus, assuming that the temperature range contemplated is 30 to 200 and the temperature at the point of shipment is 40, the difference between 40 and is 7 0, while the difference between l0 and 200 is 160. To take care of the changes of temperature within the range indicated, the evacuation should be so conducted that the head surface of the'piston under the desired pressure isabout at the dotted line P.

In order to avoid sudden fluctuations and hammer action in the tube 1, I have the connecting conduit in the crook portion 1a in the form of a capillary tube 1?), as indicated.

In the foregoing, I have described what I consider the preferred embodiment of my invention. However, it is understood that the invention may be carried out in various other ways. The invention essentially comprises a positive seal and means for permitting variations in the column of the liquid within the space confined by the seal. The relation of the sealing means and the means permitting the changes of volume may as,- sume many difierent forms.

While I have specifically described what is known as an absolute pressure gauge, the invention may find expression in various other forms of gauges. The well may be made of glass or other suitable material.

I claim:

1. In apparatus of the character described, the combination with a tube closed at the top, a well, a U-shaped connection between the well and the bottom of the tube, a liquid in the tube and partly filling the well, the well having an outlet above the level of the liquid, of means for interrupting communication between the tube and the well, resilient means operative when the said interrupting means is effective, to permit expansion of the liquid in the tube. V

2. In apparatus of the character described, the combination with a tube closed at the top, a well, a U-shaped connection between the well and the bottom of the tube, a liquid in the tube and partly filling the well, the well having an outlet above the level of the liquid, of means for interrupting communcation between the tube and the well, and resilient means operatively connected with the interrupting means for permitting, when the lattell) is effective, expansion of the liquid in the tu e. 0' "i 3. In apparatus of the character described, the combination with a tube, a well having a relatively thick bottom wall and a cylindrical depression in the bottom wall, the tube being closed at the top and having at the bottom a U-shaped connection to the bottom of said depression, and a liquid filling the tube and partly filling the well, the latter having an outlet above the level of the'liq'uid, of a piston accurately fitting the said depression and disposed above the latter, means for moving the piston into and out of the said depression, and means for permitting expansive movement of the liquid in the tube whenthe piston is disposed in the depression.

4. In apparatus of the character described, the combination with a tube, a well having a relatively thick bottom wall and a cylindrical depression in the bottom wall, the tube being closed at the top and having at the bottom a U-shaped connection to the bottom of said depression, and a liquid filling the tube and partly filling the well, the latter having an outlet above the level of the liquid, of a piston accurately fitting. the said depression and disposed above the latter, means for moving the piston into and out of the said depression and means for permitting expansive movement of the liquid in the tube when the piston is disposed in the depression, comprising. resilient means between the piston and the means for moving it.

5. In apparatus of the character described, the combination with a tube closed at the top, a well, a Ushaped connection between the well and the bottom of the tube, a liquid in the tube and in the well, the well having an outlet above the level of the liquid, of means between the bottom of the well and the level of the liquid in the well operable at Will to in-V hibit the flow of liquid from the tube into the well and means associated with the said inhibiting means for resiliently yielding to the pressure of the liquid in the tube.

In testimony whereof I aflix my signature.

HERBERT A. CLARK. 

